A classification of the tumors of the glioma group on a histogenetic basis with a correlated study of prognosis.

From 1922 to 1925 Bailey undertook extensive pathological and histological studies of brain tumors, and based on cellular configuration, he created a classification system of thirteen categories. In 1927 he reduced the number of categories to ten. German translation, 1930. Ferguson, Sherise and Maciej S. Lesniak. "Percival Bailey and the Classification of Brain Tumors," Neurosurgical Focus, 18. No. 4. (April 2005).